program convex_n_gon;
{$APPTYPE CONSOLE}
uses
  SysUtils;

type
  arrInt = array of integer;
var
n,k,i: integer;
mass: array of arrInt;
fin: textFile;
flag:boolean; 
begin
assignFile (fin, 'input.txt');
reset (fin);
readln (fin, n);
setlength (mass, n);
for i:=0 to n-1 do
  setlength (mass[i], 2);
for i:=0 to n-1 do
  read(fin, mass[i][0], mass[i][1]);
  flag:=true;
  k:=mass[n-1][0]*mass[0][1]-mass[0][0]*mass[n-1][1]+mass[0][0]*mass[1][1]-mass[1][0]*mass[0][1]+mass[1][0]*mass[n-1][1]-mass[n-1][0]*mass[1][1];
for i:=0 to n-3 do

  if (k*(mass[i][0]*mass[i+1][1]-mass[i][1]*mass[i+1][0]+mass[i+1][0]*mass[i+2][1]-mass[i+2][0]*mass[i+1][1]+mass[i+2][0]*mass[0][1]-mass[0][0]*mass[i+2][1])<0) then
    begin
    flag:=false;
    end;


  if (k*(mass[n-2][0]*mass[n-1][1]-mass[n-1][0]*mass[n-2][1]+mass[n-1][0]*mass[0][1]-mass[0][0]*mass[n-1][1]+mass[0][0]*mass[n-2][1]-mass[n-2][0]*mass[0][1])<0) then

    flag:=false;

  if (k*(mass[n-1][0]*mass[0][1]-mass[0][0]*mass[n-1][1]+mass[0][0]*mass[1][1]-mass[1][0]*mass[0][1]+mass[1][0]*mass[n-1][1]-mass[n-1][0]*mass[1][1])<0) then
    flag:=false;
  if (flag) then
    writeln ('convex')
else
  writeln ('not convex');
  close (fin);
readln;
end.


